Carburetor for internal-combustion engines



Aug. 24, 1926. 1,597,022

T. J. B. DRAYTON CARBU RETOR FOR INTERNAL COMBUSTION ENGINES Filed 001 1, 19 5 2 Shee ts-Sheet 1 jet in the choke tube.

Patented Aug. 24, 1926.

rrmornnms JAM-11s BRADLEY mmr'ro w,

PATENT OFFICE.

LONDON, .ENGLAN D.

or urrna noawoon,

CARIBUBETOB FOB INTERNAL-COMBUSTION ENGINES.

Application fled] October 1,. 1925, Serial No. 59,933, and in Great Britain September 29, 1924.

This invention comprises improvements in and connected with carburetors'for internal combustion engines, in which the float-chamber is sealed excepting for a controlled vent to the atmosphere or air supply and is connected above the liquid level with a port or ports in the induction pipe.

The object of the present invention is to provide improved means' for producing automatic variation of pressure in the float chamber, the said means being adapted for permitting the variations to be pre-determined with accuracy for ensuring correct mixture proportions at all engine speeds and loads. 4

According to this invention, the air pressure in the float chamber is varied or controlled by regulated or calibrated ports and ducts, one of which provides a suction communication between the air space of the float chamber and the induction pipe in the vicinity of the throttle or on the engine side 0 the throttle while another'provides a communication between the said air space and a port or vent concentric with the fuel spray By this means, variations in suction eifect in the induction pipe produce variations of the pressure in the float chamber which are conducive to a regu lation of the fuel feed. By a suitable predetermination of the size of the master jet and calibration of the vents or ducts, it is possible to obtain a regulation whereby the fuel flow curve will correspond with the air flow curve as required by the engine under all conditions.

. In carrying out the invention, the float chamber is sealed and provided with an air vent ofpredetermined gauge. A connection is made between the air space of the float chamber and the choke tube space, this connection being suitably made by way of a bore formed centrally in the main nozzle and a duct communicating between the said bore and the air space of the carburetor float chamber. A second connection is made by means ;:of a suitable duct between the air space bf the float chamber and the induction pipe on the engine side of the throttle or at t e place where the throttle valve is situated or at both of these places. The

f wards the-float chamber with vent in the floatchamber and the vents or ports of the saidducts are so relatively proportioned and act in such a manner as hereinafter described as to maintain a constancy in the proportion of fuel to air under different running conditions.

In order to enable the invention to be readily understood reference is made to the accompanying drawing illustrating one example of a construction embodying these improvements.

Figure 1 is a central longitudinal sectional elevation of a carburetor arrangement comprising these improvements.

Figure 2 is a transverse section on the line II- II of Figure 1, the float chamber being shown in elevation.

Figure 3 is a transverse section on the line III-III of Figure 1.

Figure 4 is a longitudinal section along the line IV-IV of Figure 5, looking tothetaper plug and attachment in elevation.

Figure 5 is a plan of Figure 1.

Figure 6 is a vertical section of the plug valve shown in Figure 2 the section being at right angles thereto and Figure 7 is a section on the line VIL-VII of Figure 6.

In the drawing, a is a sealed float chamber containing the usual float b and float valve 0 Figure 3. dis the main annular nozzle situated in the throat of the choke e and f is a known idling nozzle. The main nozzle (1 is supplied by the duct d from a well 9 in a nipple or fitting, this well being supplied from the float chamber a by way of a master fuel jet h, chamber 7', Figure 3, and port 70 Figures 2 and 3. The supply tube l for the idling nozzle 7 depends to the level of the well 9 so as to take up petrol during starting or light running in known The central stem m of the main nozzle d is hollow and opens at its upper end into the choke tube and at its lower end into a chamber 01. communicating by ducts 0 0' with the air space of the float chamber. The space 9 above the well 9 surrounds the idling nozzle chamber r and communicates with the air space of the float chamber through the port 1;.

The chamber 1' is a tubular fitting fixed into or integral with the lower portion of the tapered plug valve 8 which is kept down in its seating by a blade spring t and is adjustable by a handle u, Fig. 5.

As will be'seen from Figure 4 the plug valve 8 has a diametral port v which when in alignment with the duct or port w is the atmospheric port into the float chamber. When o is in alignment with the air admission duct w the amount of air permitted to pass from the duct w to a duct 10' is regulated by a threaded valve :0. The valve ar: regulates the amount of air flowin from the passage 'w past the idling nozzle f igure 2 to the port 5 Figure 1 by way of w a; w Figure 4, a separate axial hole 1 in the taper plug parallel with I shown in Figures 4, 6 and 7, the outer annulus 2, 1, 1, Z, 3

'and 4 Figure 2 to the port 5 Figure 1.

When the plug 8 is turned for admission of air as seen in Figure 4, a port 31 therein registers with the port of the duct w and also'with annulus 2 by way of the axial hole 1' in the taper plug. A tubular extension 2 Figure 2 of the plug carries the axial passage 1 down close to the idling nozzle f and the radial passage Z communicates by Way of passages 3 and 4 Figures 1 and 2 with the port 5 Figure 1. In the said position of the plug 8, the radial passage 2 therein aligns with the duct 3 which opens into the duct 4 running longitudinally of the choke tube and having a port 5 situated at a point where such port 5 is covered by the throttle 6 when the latter is closed as seen in Figure 1. A port 7 is situated in the induction pipe just beyond the throttle 6 and opens into a longitudinal duct 8 communicating with a transverse duct 9 which opens into the air space of the float chamber a. The port 7 may be dispensed with and the port 5 need not necessarily be closed by the closing of the throttle.

In operation and when the engine is merely turning over idle with the throttle closed or almost closed, there is strong suction on the ports 5 and 7 in the induction pipe. However, there is no reduction of pressure in the air space of the float chamber 01 'as atmospheric air is freely admitted thereto by way of the hollow stem m of the main nozzle and the passages 0, o and also by the passages 12 and 'w and w Figures 3 and 4. At higher engine speeds, there is suction on the main nozzle 03, the throttle 6 being then opened to a suitable extent but there is a reduced degree of suction on the port 5 or ports 5 and 7 in the induction pipe. Thus, atmospheric pressure may still be maintained in the float chamber but with a tendency towards reduction. At still higher engine speeds and further opening of the throttle there is strong suction on the main nozzle 03 due to the suction of the 9 supply.

engine and the velocity of the stream past the nozzle d, and a certain degree of suction on the ports 5 and 7 which arethen influenced more strongly by suction induced by the velocity of the stream, although the influence due to direct suction by the engine piston is less than before. Under these and other high speed conditions the suction at all these three points lowers the pressure in the float chamber and the port or vent a; to atmosphere above described fails to. admit suflicient air to balance the resultant suction. Consequently, a reduction of pressure Within the float chamber takes place with a corresponding reduction of the fuel With the throttle fully open and the engine running at full speed and under full load, the master fuel the correct quantity of fuel to the main nozzle d. The strong suction on the latter reduces the liquid level in the well g so that the ports in the well leading to the nozzle d become uncovered. Thereupon, air from the space q above the well passes with the liquid fuel to the nozzle d and has the effect of atomizing the fuel and producing a spray in a highly desirable condition 'for t is phase of engine running. Moreover, the air is now being sucked from the space 9 at a greater rate than it can enter through the port 12 from the float chamber. Thus, an additional source of suction is applied to the air space of the float chamber during this running condition and has the effect of preventing wasteful feed through the master jet h, and, in addition, any reduction of pressure in the space 9 below the pressure of the air space-of the float chamber has a beneficial compensating effect upon the fuel feed through-the master jet k.

If the engine is overloaded and the throttle 6 is wide open, the port 5 or ports 5 and 7 and the nozzle (Z are influenced by a reduced resultant suction. Consequently, a rise of pressure towards that of the atmosphere takes placein thefloat chamber and the fuel remains constant by weight in proportion to the reduced air flow, whereas without these improvements the fuel flow would fall off under such conditions. The means above described are so simple and sensitive that there is no delay or lag in the regulating action hereinbefore described when a, change in engine running conditions occurs.- Calibrated replaceable vents or alternatively adjustable vents may be fitted at any or all points '0, 7, 5 and m or they may be of fixed size. In any construction, the vents and ports are so co-ordinated that with the engine running light there is no reduction of pressure in the float chamber the pressure remaining atmospheric on the balance. With high speeds, however, reduction of pressure in the float chamber takes jet h passes only just- -jet can readily be found which gives the correct flow for maximum engine demands and the proportions of fuel to air by weight will then be correct under all conditions.

The master fuel jet may remain the same over a narrow range of requirements and, if too large in any case, its effect may be reduced by increasing the size of the vent through the hollow stem m in the main nozzle d which will increase the float depression at high speeds or if too small its effect may be increased by reducing the size of the vent. The other vents such as the vents c or 'w, and the ports 5 and 7, however, must then be varied so as to restore the atmospheric balance condition when the engine is idling or the constancy of proportion by weight of fuel to air will be upset. Means may be provided for closing the valve 8, and so closing the direct vent on the float chamber, sa1d means being employed as a control for weakening the mixture when running an open throttle or for cutting ofl the fuelsupply entirely when coasting with open throttle. As will be seen from the drawing, it is possible by operating the handle a to turn the plug 8 so that it cuts off the air vent q) and incidentally also closes communication between the port 5 and the idling nozzle 7.

I claim 1. A carburetor for internal combustion engines comprising in combination a float chamber having a restricted vent for air admission thereto, an induction pipe, a throttle therein, a duct connecting between the air space of said float chamber and a port in the vicinity of the throttle in the induction pipe, said port being open under all running conditions, a main jet tube, a vent tube concentric with the main jet tube and presenting a vent orifice concentric with the orifice of said jet tube, and a duct connecting between said vent tube and the .air space of said float chamber, the port and,

vents being co-ordinated so as to obtain an automatic regulation of the fuel feed under different running conditions.

2. A carburetor for internal combustion engines comprising in combination a float chamber having a restricted vent for air admission thereto, an induction pipe, a throttle therein, a duct connecting between the air space of said float chamber and a port in the vicinity of the throttle in the induction pipe, said port being open under all running conditions, a main jet tube, a vent tube disposed within the main jet tube and presenting a vent orifice within the jet jet tube said vent .bination of a main diffuser jet tube,

orifice, and a duct connecting between said vent tube and the air space ofsaid float chamber, the port and vents being co-ordinated so as to obtain an automatic regulation of the fuel feed under different run ning conditions.

3. A carburetor for internal combustion engines comprising in combination a float chamber, a well in communication with the lower part of said chamber, an auxiliary jet device disposed for the taking of its liquid fuel supply from the upper part of said well, an induction pipe, a throttle therein, a duct communicating between said auxiliary jet device and a port in the induction pipe said port being disposed so as to be closed by the throttle when the latter is in the closed condition, a main diffuser jet tube, a duct connecting said jet tube with the lower part of said well, a vent tube within said tube presenting a vent orifice concentric with the diffuser jet orifice, a duct connecting said vent tube with the air space of the float chamber, air admission means in connection with said float chamher said means being adapted for restricting said admission, and a duct communicating between the air space of the float chamber .and a port disposed in the induction tube on the engine side of the throttle, the ports and vents being co-ordinated so as to obtain an automatic regulation of the fuel feed under different running conditions.

4. In a carburetor for internal combustion engines of the type comprising a float chamber, an induction tube, a throttle in the latter, a restricted vent from the atmosphere to the air space of the float chamber and a duct communicating between the said air space and a port in the induction tube in the neighbourhood of the throttle, the coma well, a master jet controlling the passage offuel from the float chamber to said well, a duct leading from the lower part of said well to the main diifuser jet tube, a vent tube concentric with said jet tube and presentin a vent orifice in the vicinity of the jet ori ce, a duct connecting said vent tube with the air space'of said float chamber, an auxiliary jet chamber in communication with said well said chamber being in communication with the air space of the float chamber through a small port, and an auxiliary jet device-disposed for taking its supply from the upper part of said well, the ports and vents being co-ordinated so as to obtain an automatic regulation of the fuel under different running conditions.

5. In a carburetor for internal combustion engines of the type comprising a float chamber, an induction tube, a throttle in the latter, a restricted vent from the atmos phere to the air space of the float chamber and a duct communicating between the said air space and a port in the induction tube float chamber, a vent tube concentric with in the neighbourhood of the throttle, the said main jet tube and presenting a vent combination of an auxiliary jet device, a orifice in the vicinity of the main jet ori- 10 main diffuser jet tube, a valve device lice, and a duct communicating between said adapted for the simultaneous control of the vent tube and the air space of the float chamdelivery from said auxiliary jet and the her.

said restricted vent from atmosphere to THEOPHILUS JAMES BRADLEY N- 

